Hitherto, photoconductive cells most widely use CdS in the form of a sintered body, although CdS can be used in the form of single crystal and also in the form of a deposited thin film. In addition to CdS, ZnS, CdSe, GaAs, Si, Ge, PdS, InSb, Se, CdTe, PdSe, PdTe, Sb.sub.2 S.sub.3, PbO and ZnO are used. To improve the photoconductivity, Ag, Cu, Cl, Ga or Sb is added to the materials.
When light is irradiated for a long time, the conventional photoconductive cell is deteriorated so that its resistance changes. Then, the conventional photoconductive cell has poor reliability.
In addition, it is widely desired to provide a photoconductive cell with higher photosensitivity.